Heat exchanger assembly

ABSTRACT

A heat-exchanger end plate assembly is shown to comprise a metal plate member embodying a heat-conductive layer and a surface layer of solder, the plate having a plurality of apertures in which metal tubes are disposed. The solder layer is adhered to the tubes completely around the tube peripheries for sealing the apertures around the tubes. Where the heat-conductive layer material is formed of a material which is incompatible with the solder material at the melting temperature of the solder material, as where the heat-conductive layer is formed of copper and the solder has a copper constituent, an intermediate metal layer of steel or the like is metallurgically bonded to the heatconductive layer and is adhered to the solder layer. A method for making the heat exchanger assembly is also shown.

Hingorany HEAT EXCHANGER ASSEMBLY Aug. 7, 1973 Primary Examiner-ManuelA. Antonakas Assistant Examiner-Theophil W. Streule, Jr.

1 P t C t, R1. [75] Inventor Ashok mngonny aw u kc Atrorney-HaroldLev1ne,Edward J.Connors,.lr.,.iohn [73] Assignee: Texas InstrumentsIncorporated, and James McAndmws Dallas. Tex.

[57] ABSTRACT [22] Filed: 1968 A heat-exchanger end plate assembly isshown to com- [21] Appl. No.: 787,718 prise a metal plate memberembodying a heatconductive layer and a surface layer of solder, theplate having a plurality of apertures in which metal tubes are III.l65/l78ii l disposed The solder layer is adhered to the tubes I 58]Fie'ld 99 197 pletely around the tube peripheries for sealing the aper-5 5 2 tures around the tubes. Where the heat-conductive layer materialis formed of a material which is incompatible with the solder materialat the melting tempera- [56] Reterences cued ture of the soldermaterial, as where the heat UNITED STATES PATENTS v conductive layer isformed of copper and the solder has 625,117 5/1899 Martin 29/199 X acopper constituent, an intermediate metal layer of 948,373 2/1910165/172 X steel or the like is metallurgically bonded to the heatz l gconductive layer and is adhered to the solder layer. A 3'065539 ""9622:11;; 29/199 X method for making the heat exchanger assembly is also3,207,215 9/1965 Whittell, Jr.... 165/178 x showm Brown et al. 7 C i s,3 ra g F gures HEAT EXCHANGER ASSEMBLY Prior to the present invention,heat exchanger end plate assemblies embodying a multiplicity of coppertubes sealed within respective apertures in a copper end plate have beenformed by disposing the tubes in respective apertures and by depositingsufficient solder material in molten condition around each tubeperiphcry to secure the tube in its respective plate aperture forsealing the aperture. As will be understood, such end plate assembliescan be mounted at the end of a tank containing heat-exchanger fluid withthe periphery of the end plate sealed to the tank so that the tubesextend from the tank in sealed relation to the plate. When theabove-described method of end plate assembly has been used, the methodhas been expensive and time-consuming and has resulted in rejection of alarge proportion of the assemblies produced by the method due to leakingof fluid around the periphery of one or more tubes in each assembly.

It is an object of this invention to provide a novel and improved platematerial for use in making heatexchanger end plate assemblies; toprovide such a novel and improvedplate which can be used for formingsuch assemblies in an inexpensive and convenient manner with highreliability; to provide novel and improved heat-exchanger end plateassemblies.

Briefly described, the novel and improved plate material of thisinvention comprises a plurality ofmetal layers which are bondedtogether. to form a laminate, the material having one layer which isselected for its high heat-conductivity properties and another surfacemetal layer which is formed of solder material. Preferably, where themetal of high heat-conductivity is incompatible with the solder layermaterial at the melting temperature of the solder material, the platematerial incorporates an intermediate metal layerwhich ismetallurgically bonded to the metal layer of high heatconductivity andwhich is adhered to the solder layer. In forming a heat-exchanger endplate assembly utilizing this novel and improved plate material, aplurality of metal tubes are disposed in respective apertures formed inthe plate material. The plate material and tubes are then heated formelting the solder material of the plate so that the solder materialadheres to the tubes completely around the peripheries of the tubes forsealing the tubes within the plate aperturesPreferably the plate andtubes are heated by applying heat thereto from the side opposite thesolder layer of the plate material so 'that the solder material, as itis melted, is drawn into .the plate apertures around the tubeperipheries bycapillary action. 1 Other objects, advantages and detailsof the nove and improved plate materials, assemblies and'methods of thisinvention appear in the following detailed description of preferredembodiments of the invention, the detailed description referring to thedrawings in which:

FIG. 1 .is a perspective view of the, heat-exchanger end plate assemblyof this invention; FIG. 2 is a side elevation view of the novel platematerial of this invention; and i FIG. 3 is a partial section view toenlarged scale along line 3-3 of FIG. 1.

Referring to the drawings, in FIG. 2 indicates a preferred embodiment ofthe novel and improved plate material of this invention which is shownto include a surface metal layer 16 formed of a solder material, an

intermediate metal layer 18, and a metal layer 20 formed of a materialof selected, relatively high heatconductivity properties. In accordancewith this invention, the intermediate metal layer is preferablypressure-welded or rol1-bonded to the metal layer 20 by any conventionalmeans, such as described in U. S. Pat. No. 2,691,815 issued to H.Boessenkool et al on Oct. 10, 1954, so that the layer 18 ismetallurgically bonded to the layer 20. That'is, the metal layer 18 ispreferably bonded to the layer 20 by means of interatomic attractiveforces between the materials of the layers 18 and 20. The metal layer 16may also be pressure-welded or roll-bonded to the intermediate layer 18,if desired, but can also be adhered to the intermediate layer byapplying molten solder material of layer 16 to the intermediate layerand by permitting the solder material to cool and solidify in situ onthe intermediate layer 18. In this way, the metal layers I6, 18 and 20are each bonded together to form the composite laminate plate material10.

In accordance with this invention, the metal layer 20 of the platematerial 10 may be formed of any metal material of suitableheat-conductivity properties, but is preferably formed of copper. Thesolder layer of the plate material 10 can also be formed of any suitablematerial of low melting temperature within the scope of this inventionbut is preferably formed of a copperbearing solder alloy selected fromthe group consisting of an alloy embodying about 72-percent silver, and28 percent copper, an alloy embodying about45 percent silver, 15 percentcopper, 16 percent zinc and 24 percent cadmium and an alloy embodyingabout 52 percent silver, 16 percent copper, 15.5 percent zinc and 16.5percent cadmium. The intermediate layer 18 may be formed of any suitablesolderable material which can be bonded to the material of layer 20, thematerial of layer 18 being selected to be compatible with the soldermaterial at the melting temperature of the solder material. For example,where the-metal layer 20 is formed of copper and the solder layer has acopper constituent, the intermediate layer 18 is preferably formed ofsteel. The layer 18 can be formed of any steel, nickel, nickel alloy orthe like within the scope of this invention. In this regard, note thatthe term com-. patible as used herein means that the material of layer18 does nottend to dissolve into or to alloy with the solder material oflayer I6-to any significant extent when the solder material is melted incontact with the intermediate layer 18. In a preferred embodiment of theplate material 10, the metal layer 20 can beof any desired thickness,but the solder layer 16 is preferably kept within the range of thicknessfrom about 0.002 inches to 0.060 inches while the thickness of theintermediate layer 18 is preferably kept in the range from 0.001 to0.005 inches.

In accordance. with this invention as illustrated in FIG. I, the platematerial 10 is provided with a plurality.

of apertures 14 in any conventional manner and the metal tubes 12 arerespectively disposed in the plate apertures. As illustrated, the plateapertures extend through each of the layers of the plate material andare of a proper size to snugly receive the tubes 12 therein. In apreferred embodiment of this invention, where the plate materialembodies layers of copper, steel and copper-bearing solder as abovedescribed, the tubes 12 are also preferably formed of copper. Inaccordance with this invention, the plate 10 and tubes 12 are thenheated in any conventional manner for melting the solder layer 16 of theplate material so that the solder material flows into the plateapertures 14 around the peripheries of the tubes 12 for adhering to thetubes completely around the tube peripheries, thereby to seal the plateapertures around the tubes. Preferably as indicated by the arrow 22 inFIG. 3, the plate and tubes 12 are heated from the side of the plateopposite from the solder layer 16 of the plate material. Thisestablishes a temperature differential between the opposite sides of theplate 10 with the higher temperature side being opposite from the solderlayer side of the plate. This facilitates drawing of the melted soldermaterial 16 into the plate apertures 14 by capillary action as isillustrated in FIG. 3. As will be understood, the solder material isthereafter permitted to cool and solidify to form the heat-exchanger endplate assembly 24 illustrated in FIG. 1.

It will be understood that, in the method above described, a very largenumber of tubes 12 can be embodied in closelyspaced side-by-siderelation extending through a plate member but that the tubes can all besimultaneously and uniformly soldered in the respective plate memberapertures in a single heating and cooling operation. This issubstantially less expensive and is much more convenient than the priorart process for forming such heat-exchanger end plate assemblies. Mostimportant, the method of this invention is much more reliable than theprior art process and consistently produces assemblies which areleak-free as initially formed and which remain reliably leak-free duringlong periods of use. In this regard, it will be understood that, wherethe plate 10 embodied in the assembly is relatively large, somedifficulty may be experienced in heating the assembly componentsuniformly so that the solder material 16 reaches melting temperature onall parts of the plate at approximately the same time. However, in usingthe plate material 10 as above described, the intermediate layer 18 ofthe plate is selected for its compatibility with the solder material sothat, even though molten solder material may be in contact with theintermediate layer on one portion of the plate for a substantial periodof time while the solder is being melted on other portions of the plate,no significant dissolution of the intermediate layer 18 and nosignificant alloying between the materials of layer 16 and 18 can occur.In this regard note that where the heat-conductive layer 20 is formed ofcopper as above described, such a material would be incompatible with acopper-bearing solder in the plate layer 16. If the molten soldermaterialwere permitted to contact the heat-conductive layerforanyappreciable period of time, some dissolution of the heat-conductivelayers could occur and alloying between the heat-conducting layermaterial and the solder material could undesirably raise or lower themelting temperature of the solder. However, when the intermediate layermaterial 18 is selected in the manner above described such dissolutionof the plate materials and such altering of the solder meltingtemperature are avoided.

It should be understood that although a particular three-layerembodiment of the plate material of this invention has been describedabove by way of illustration, plate materials having other number oflayers are also within the scope of this invention. For example,particularly where small plate members which can be uniformly heated atone time are used, the intermediate layer 18 may be omitted from theplate material 10 so that the solder surface layer I6 is bonded directlyto the heat-conductive layer 20 of the plate material. Alternatively,solder layer 16 could be bonded directly to the heat conductive layer 20on both sides of the heatconductive layer. Further, intermediate layers18, each bonded to respective solder layers 16 could be metallurgicallybonded to the heat-conductive layer 20 at respective opposite sides ofthe heat-conductive layer within the scope of this invention. It shouldbe understood that this invention includes all modifications andequivalents of the illustrated plate materials, methods and assemblieswhich fall within the scope of the appended claims.

I claim:

1. A heat exchanger end plate assembly comprising a metal plate memberembodying a plurality of metal layers bonded together to form alaminate, said plate member including a metal layer of selected heatconductivity properties and at least one surface metal layer of soldermaterial, said plate member having a plurality of apertures thereinextending through each of said layers, and a plurality of metal tubesrespectively disposed in said plate member apertures, said solder layermaterial of said plate member extending through the lengths of saidapertures and being adhered to said tubes completely around theperipheries of said tubes for sealing said apertures around said tubes.

2. An assembly as set forth in claim I wherein said plate memberembodies a single solder layer bonded to said layer of selectedheat-conductivity properties and wherein said metal tubes each extendfrom opposite sides of said plate member.

3. An assembly as set forth in "claim 1 wherein said plate member layerof selected heat-conductivity properties is incompatible with said platemember solder layer material at the melting temperature of said soldermaterial, said plate member embodying an intermediate metal layer ofsolderable material which is compatible with said solder material at themelting temperature of said solder material, said intermediate layerbeing metallurgically bonded to said layer of selected heatconductivityproperties and adhered to said plate member solder layer and whereinsaid metal tubes each extend from opposite sides of said plate member.

4. An assembly as set forth in claim 3 wherein said plate member layerof selected heat-conductivity properties is formed of copper, saidsolder layer embodies an alloy having copper as a constituent thereof,and said intermediate layer is formed of steel, said tubes being formedof copper.

5. An'assembly as set forth in claim 4 wherein said solder layercomprises a material selected from the group consisting of an alloyembodying about 72 percent silver and 28 percent copper, an alloyembodying about 45 percent silver, 15 percent copper, 16 percent zincand 24 percent cadmium, and an alloy embodying about 52 percent silver,16 percent copper, 15.5 percent zinc and 16.5 percent cadmium.

6. An assembly as set forth in claim 1 wherein said plate memberembodies a solder surface layer adhered to each side of said platemember layer of selected heat-conductivity properties.

7. An assembly as set forth in claim I wherein said plate member layerof said selected heat-conductivity properties is incompatible with saidplate member solder layer material, said plate member embodying anintermediate layer of solderable material metallurgically mediate layersof said plate member and wherein said bonded to each side of platemember layer of selected metal tubes each extend from opposite sides ofsaid heat-conductivity properties, said plate member having platemember.

a layer of solder material adhered to each of said inter-

2. An assembly as set forth in claim 1 wherein said plate memberembodies a single solder layer bonded to said layer of selectedheat-conductivity properties and wherein said metal tubes each extendfrom opposite sides of said plate member.
 3. An assembly as set forth inclaim 1 wherein said plate member layer of selected heat-conductivityproperties is incompatible with said plate member solder layer materialat the melting temperature of said solder material, said plate memberembodying an intermediate metal layer of solderable material which iscompatible with said solder material at the melting temperature of saidsolder material, said intermediate layer being metallurgically bonded tosaid layer of selected heat-conductivity properties and adhered to saidplate member solder layer and wherein said metal tubes each extend fromopposite sides of said plate member.
 4. An assembly as set forth inclaim 3 wherein said plate member layer of selected heat-conductivityproperties is formed of copper, said solder layer embodies an alloyhaving copper as a constituent thereof, and said intermediate layer isformed of steel, said tubes being formed of copper.
 5. An assembly asset forth in claim 4 wherein said solder layer comprises a materialselected from the group consisting of an alloy embodying about 72percent silver and 28 percent copper, an alloy embodying about 45percent silver, 15 percent copper, 16 percent zinc and 24 percentcadmium, and an alloy embodying about 52 percent silver, 16 percentcopper, 15.5 percent zinc and 16.5 percent cadmium.
 6. An assembly asset forth in claim 1 wherein said plate member embodies a solder surfacelayer adhered to each side of said plate member layer of selectedheat-conductivity properties.
 7. An assembly as set forth in claim 1wherein said plate member layer of said selected heat-conductivityproperties is incompatible with said plate member solder layer material,said plate member embodying an intermediate layer of solderable materialmetallurgically bonded to each side of plate member layer of selectedheat-conductivity properties, said plate member having a layer of soldermaterial adhered to each of said intermediate layers of said platemember and wherein said metal tubes each extend from opposite sides ofsaid plate member.